docs: add blurb about target audience to maintainer-profile

It's good to be clear about who the intended target audience for any
given piece of documentation is, as this will help us put new text in
the correct place. Let's encourage submitters to state it explicitly
rather than relying on where they placed it in the directory hierarchy
as there isn't necessarily a one-to-one correspondence between them.

Target audience: documentation contributors and reviewers.

Signed-off-by: Vegard Nossum <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/doc-guide/maintainer-profile.rst

···
 introduced.  Generating HTML documents and looking at the result will help
 to avoid unsightly misunderstandings about how things will be rendered.
 
+All new documentation (including additions to existing documents) should
+ideally justify who the intended target audience is somewhere in the
+changelog; this way, we ensure that the documentation ends up in the correct
+place.  Some possible categories are: kernel developers (experts or
+beginners), userspace programmers, end users and/or system administrators,
+and distributors.
+
 Key cycle dates
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